如何在邻居列中插入id的数量？

Question

我有一个具有这种结构的表：

+----+-------------------+
| id | identical_with_id |
+----+-------------------+

id是自动递增的，我需要在此列identical_with_id中插入与id的值完全相同的值。我怎么能这样做？

我想要这样的事情：

+----+-------------------+
| id | identical_with_id |
+----+-------------------+
| 1  | 1                 |
| 2  | 2                 |
| 3  | 3                 |
+----+-------------------+

注意，实际上该表还包含identical_with_id列的其他一些值，如下所示：

+----+-------------------+
| id | identical_with_id |
+----+-------------------+
| 1  | 1                 |    -- it is a question
| 2  | 1                 |    -- it is the answer of the above question
| 3  | 1                 |    -- it is the answer of the above question
| 4  | 4                 |    -- it is a question
| 5  | 4                 |    -- it is the answer of the above question
| 6  | 6                 |    -- it is a question
| 7  | 7                 |    -- it is a question
| 8  | 7                 |    -- it is the answer of the above question
| 9  | 7                 |    -- it is the answer of the above question
+----+-------------------+

现在我需要在表格中插入一个问题。我想知道如何填写此专栏：identical_with_id？

Answer 1

无需更新表格。您可以在单个插入查询中执行此操作，如下所示。

INSERT INTO `table_name` VALUES(NULL, (SELECT `AUTO_INCREMENT` FROM  INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA = 'database_name' AND TABLE_NAME = 'table_name'));

虽然我没有注意到这一点......